The influence of timing of administration of peroperative alfentanil on pain and analgesic requirements after surgery was studied in 60 patients undergoing total abdominal hysterectomy with or without bilateral salpingo-oophorectomy. Thirty patients received alfentanil 7.5 mu g.kg(-1) on induction of anaesthesia, followed by alfentanil 7.5 mu g.kg(-1) 90s before surgical incision (group A). Thirty control patients received alfentanil 15 mu g.kg(-1), 10 min after abdominal incision (group B). In addition, 10 min after surgical incision both groups received morphine 0.2 mg.kg(-1), given over a 10 min period. The visual analogue scores (median, interquartile range) for pain 24 h after operation were 28.5 mm (11.25-47.0) in group A and 21.0 mm (10.5-47.5) in group B, p = 0.76. There were no differences in visual analogue scores at intermediate times. Morphine consumption in the first 24 h after surgery (median, interquartile range) was 53.5 mg (37.25-60.0) in group A and 52.0 mg (39.75-71.0) in group B, p = 0.52. We conclude that postoperative morphine consumption and pain scores ale no different when alfentanil 15 mu g.kg(-1) is given before or after skin incision for abdominal hysterectomy.